I just got the Canon EOS R and I am literally so excited to start taking photos but I am honestly so lost when it comes to the lenses. The camera came with this one lens that zooms in and out but when I take pictures of my sister the background isnt really blurry like those professional ones you see on instagram and I really want that look for her graduation pictures next month. I have no idea where to start and sorry if this is a dumb question but I am basically a total baby at this stuff and everything feels very overwhelming right now.

I was looking online and there are all these numbers like 50mm and 85mm and then the f/1.8 or f/2 stuff and I have no clue what any of that actually means for the actual photo. My logic was that maybe a bigger number is better? But then I saw a video saying 50mm is the best for beginners because it sees like a human eye does but then someone else said 85mm is way better for faces because it doesnt make people look weird or stretched out so I am just sitting here staring at my screen getting more confused by the second.

I really cant spend more than like 300 or maybe 400 dollars max because the camera itself was already a huge splurge for me and my bank account is crying a little bit lol. I also dont really understand if I need an adapter or what that even is? People keep talking about EF lenses vs RF lenses and I dont want to buy something that wont even click onto my camera or needs an extra part that costs another hundred bucks. I saw this RF 50mm f1.8 lens that looks pretty cheap and small which is nice but then I saw a used 85mm one and I dont know if buying used is a bad idea for someone who doesnt know how to check if it is broken or not. I just want my photos to look pretty and have that soft look in the back without breaking the bank or buying the wrong thing... so what should I actually be looking for?